Electric vehicles present a growing application for rechargeable batteries and, in particular, for large battery packs. Such an application, however, presents a number of engineering challenges to the power system designer, primarily due to the need to balance the expectations of the consumer with the system requirements and the constraints placed on the system by the batteries within the battery pack. Consumer expectations include those associated with the vehicle as a whole, e.g., vehicle range, performance and reliability, and those that are specific to the vehicle's battery system, e.g., battery pack lifetime and replacement cost, as well as the time, cost and convenience associated with charging the vehicle. System requirements include power output, battery pack weight and reliability. Battery constraints include those associated with charging, operational, and storage temperatures; charge rates; the level of allowed/preferred charging (i.e., 75% of full charge, full charge, over-charged, etc.); and the level of discharge allowed before charging.
To address some of the issues associated with batteries, sophisticated charging algorithms may be employed. For example, co-assigned U.S. Pat. No. 8,054,038 discloses a system for controlling the charging system of an electric vehicle, more specifically the charging level, based on a number of parameters. Disclosed parameters include expected travel distance, road conditions, weather conditions, desired battery power safety margins and driving style. Co-assigned U.S. Pat. No. 7,782,021 discloses an alternate charging system controller that determines the optimal time to charge a battery pack based on charging cost, thus taking into account variations in the cost of electricity based on the time of day. Co-assigned U.S. Pat. Nos. 7,671,567 and 7,629,772 disclose alternate charging system controllers that determine the optimal cut-off voltage to be used during charging based on desired vehicle performance and intended usage, driving range and battery life.
While the prior art charging system controllers may take into account a variety of factors in determining optimal charge rates, charge levels, and charging times, these systems provide the user with limited ability to control the charging schedule. As a result, these system controllers do not help the user to minimize the costs associated with charging their vehicle, and therefore do not fully meet consumer expectations with regards to convenience and the potential savings associated with owning an electric vehicle. Accordingly, what is needed is a user interface for a battery pack recharging system that simplifies vehicle charging while helping the user to minimize charging costs. The present invention provides such a use interface and charging system controller.